1. Field of the Invention
The present invention relates to an illumination device for illuminating an original, and an image reading apparatus using the device as illumination means.
2. Related Background Art
An image reading apparatus comprises illumination means for illuminating a film original such as a negative film, reversal film, elongated film, or the like, convey means for conveying the film original, image reading means for reading an image on the film original by receiving light transmitted through the film original, and outputting an image signal, and image processing means for performing arithmetic processing of data of the image read by the image reading means. The image reading apparatus is used for capturing an image on a film original into a so-called personal computer or the like.
A color image is normally read by switching three colors, i.e., red (R), green (R), and blue (B). When small dust particles, scratches, and the like are present on the film original, they appear as black dots (in case of a positive film) or white dots (in case of a negative film) on the read image, thus deteriorating the image quality.
In order to solve such problem, a technique for detecting dust, scratches, and the like on a film original using the feature of infrared rays has been proposed (for example, Japanese Patent Laid-Open Application No. 63-116551). In this case, the image reading apparatus must be capable of reading using infrared rays (IR) in addition to normal reading using three colors, i.e., red (R), green (R), and blue (B).
More specifically, the image reading apparatus which can read using infrared rays (IR) must have light sources that output four color light beams, i.e., red (R), green (R), blue (B), and infrared (IR) light beams.
As is well known, the image reading apparatus must meet compact and low-cost requirements. Even when the apparatus is designed to read using infrared rays (IR), it must be capable of normal reading using three colors.
Hence, an illumination device that can output four color light beams must solve a problem that pertains to the positional relationship upon aligning the beam positions of light beams output from four color light sources in association with a size reduction, in addition to realization of a compact and low-cost arrangement.
It is an object of the present invention to provide an illumination device which can output visible light and infrared light, and an image reading apparatus using the device as illumination means.
An illumination device according to the present invention comprises a visible light emitting element for emitting visible light, an infrared light emitting element for emitting infrared light, a board including a first mounting portion on which elements including at least the visible light emitting element are mounted in array and a second mounting portion on which elements including at least the infrared light emitting element are mounted in array, and a dichroic mirror which is configured and disposed to reflect light emitted by the visible light emitting element mounted on the first mounting portion by a first surface thereof, reflect light emitted by the infrared light emitting element mounted on the second mounting portion by a second surface thereof, and send light beams coming from the first and second surfaces onto a common optical path.
As described above, the first mounting portion on which elements including at least the visible light emitting element are mounted in array and the second mounting portion on which elements including at least the infrared light emitting element are mounted in array are formed on the board, and light emitted by the visible light emitting element mounted on the first mounting portion and light emitted by the infrared light emitting element mounted on the second mounting portion are adjusted and output by the dichroic mirror to propagate along a common optical path. Hence, from the viewpoint of the dichroic mirror on the optical axis, the light beams output from the visible and infrared light emitting elements appear to come from an identical location. In addition, since the visible and infrared light emitting elements are mounted in array, the illumination device can be rendered compact.
In this illumination device, the dichroic mirror may be formed so that the first surface transmits the infrared light therethrough. Also, the dichroic mirror may be formed so that the second surface transmits the visible light therethrough. The visible light emitting element may be at least one of red, green, and blue light emitting elements.
The above illumination device preferably further comprises a diffusion plate disposed in the common optical path to diffuse the visible light, since illumination nonuniformity can be improved.
In the illumination device of the present invention, it is effective to mount a light emitting element, an amount of light of which must be increased, on one of the first and second mounting portions that is closer to a light exit side of the first and second mounting portions in consideration of reflection losses in the dichroic mirror.
In the illumination device of the present invention, when the visible light emitting element comprises three different elements, i.e., red, green, and blue light emitting elements, the layout of these light emitting elements can be flexibly designed in correspondence with the characteristics of the respective elements. More specifically, layouts in the following examples are available.
For example, the light emitting element mounted on one of the first and second mounting portions that is closer to a light exit side than the other includes the infrared and red light emitting elements, and the light emitting element mounted on the mounting portion farther from the light exit side includes the blue and green light emitting elements. In another example, the light emitting element mounted on one of the first and second mounting portions that is closer to a light exit side includes the infrared and blue light emitting elements, and the light emitting element mounted on the mounting portion farther from the light exit side includes the red and green light emitting elements. In still another example, the light emitting element mounted on one of the first and second mounting portions that is closer to a light exit side includes the infrared light emitting element, and the light emitting element mounted on the mounting portion farther from the light exit side includes the red, blue, and green light emitting elements. In yet another example, the light emitting element mounted on one of the first and second mounting portions that is closer to a light exit side includes the infrared, red, and green light emitting elements, and the light emitting element mounted on the mounting portion farther from the light exit side includes the blue light emitting element.
As a preferred example, when the infrared light emitting element used in illumination for detecting, e.g., a scratch on an original is mounted on the inner side of the array on the first mounting portion, and the green light emitting element that emits green light which is a color the human eye can recognize best of the visible light emitting elements including three different elements, i.e., red, green, and blue light emitting elements, is mounted on the inner side of the array on the second mounting portion, infrared light and green light can illuminate to have nearly the same distributions. Hence, a color to which the human eye is most sensitive can be corrected more accurately. Also, when the infrared light emitting element used in illumination for detecting, e.g., a scratch on an original is mounted on the outer side of the array on the first mounting portion, and the green light emitting element that emits green light to which the human eye is most sensitive of the visible light emitting elements including three different elements, i.e., red, green, and blue light emitting elements, is mounted on the outer side of the array on the second mounting portion, infrared light and green light can illuminate to have nearly the same distributions. Therefore, a color to which the human eye is most sensitive can be corrected more accurately.
In the illumination device of the present invention, a rod-like optical member for converting light entering from one end thereof into linear output light is preferably disposed in the common optical path, since an illumination device can have a simple arrangement, and a compact linear illumination device can be realized. In addition, since diffuse illumination is made, illumination nonuniformity can be eliminated.
Also, when the illumination device comprises a rod-like optical member for converting light entering from one end thereof into linear output light, a light emitting lamp disposed at one end of the rod-like optical member to selectively emit first visible light and second visible light, and an infrared light emitting lamp disposed at the other end of the rod-like optical member to emit infrared light, a compact linear illumination device can be realized. Furthermore, since diffuse illumination is made, illumination nonuniformity can be eliminated.
The present invention is further directed to an image reading apparatus.
An image reading apparatus according to one mode of the present invention comprises an illumination device for illuminating an original, a convey device for conveying the original, an image reading device for reading an image on the original upon receiving light transmitted through the original, and outputting an image signal, and an image processing device for arithmetically processing data of the image read by the image reading device. In this apparatus, the illumination device comprises a visible light emitting element for emitting visible light, an infrared light emitting element for emitting infrared light, a board including a first mounting portion on which elements including at least the visible light emitting element are mounted in array and a second mounting portion on which elements including at least the infrared light emitting element are mounted in array, a dichroic mirror which is configured and disposed to reflect light emitted by the visible light emitting element mounted on the first mounting portion by a first surface thereof, reflect light emitted by the infrared light emitting element mounted on the second mounting portion by a second surface thereof, and send light beams coming from the first and second surfaces onto a common optical path, and a diffusion plate disposed in the common optical path to diffuse light leaving the dichroic mirror.
In this image reading apparatus, the dichroic mirror adjusts and outputs light beams emitted by the visible and infrared light emitting elements mounted in array on the board in the illumination device so that they propagate along a common optical path, and the diffusion plate diffuses and radiates these light beams, thus illuminating an original. Hence, when the illumination device illuminates a film, since outgoing light beams from the visible and infrared light emitting elements are output toward a nearly equal location on the original, illumination nonuniformity can be eliminated.
An image reading apparatus according to another mode of the present invention comprises an illumination device for illuminating an original, a convey device for conveying the original, an image reading device for reading an image on the original upon receiving light transmitted through the original, and outputting an image signal, and an image processing device for arithmetically processing data of the image read by the image reading device. In this apparatus, the illumination device comprises a visible light emitting element for emitting visible light, an infrared light emitting element for emitting infrared light, a board including a first mounting portion on which elements including at least the visible light emitting element are mounted in array and a second mounting portion on which elements including at least the infrared light emitting element are mounted in array, a dichroic mirror which is configured and disposed to reflect light emitted by the visible light emitting element mounted on the first mounting portion by a first surface thereof, reflect light emitted by the infrared light emitting element mounted on the second mounting portion by a second surface thereof, and send light beams coming from the first and second surfaces onto a common optical path, and a rod-like optical member disposed in the common optical path to convert light leaving the dichroic mirror and entering from one end thereof into linear output light.
In this image reading apparatus, the dichroic mirror adjusts and outputs light beams emitted by the visible and infrared light emitting elements mounted in array on the board in the illumination device so that they propagate along a common optical path, and the diffusion plate diffuses and radiates these light beams, thus illuminating an original. Hence, when the illumination device illuminates a film, since outgoing light beams from the visible and infrared light emitting elements are output toward a nearly equal location on the original, illumination nonuniformity can be eliminated.
An image reading apparatus according to still another mode of the present invention comprises an illumination device for illuminating an original, a convey device for conveying the original, an image reading device for reading an image on the original upon receiving light transmitted through the original, and outputting an image signal, and an image processing device for arithmetically processing data of the image read by the image reading device. In this apparatus, the illumination device comprises a rod-like optical member for converting light entering from an end portion thereof into linear output light, a light emitting lamp for selectively outputting first visible light and second visible light to one end of the rod-like optical member, and an infrared light emitting lamp for outputting infrared light to the other end of the rod-like optical member.
In this image reading apparatus, the rod-like optical member in the illumination device converts the first and second visible light beams selectively output from a light emitting lamp and incoming from its one end, and infrared light output from the infrared light emitting lamp and incoming from the other end into linear output light, thus illuminating an original. When the illumination device illuminates a film, the visible light and infrared light can be output toward an identical location on the original since their illumination nonuniformity is eliminated. Hence, image processing can be implemented more appropriately.
In the image reading apparatus of each mode, the image processing device may comprise a detection device for detecting foreign matter present on the original from data read using the infrared light. In this case, the image processing device may further comprise an alarm generation device for outputting an alarm signal upon detection of the presence of foreign matter on the original.
In this image reading apparatus, the image processing device preferably further comprises a correction device for, when the presence of foreign matter on the original is detected, correcting data at a position of foreign matter using visible light data near the position upon arithmetically processing data read using the visible light.